This invention relates to spinning units for an open-end spinning machine and, more particularly, to prevention of entrance of once discharged dirt and flies into the rotors of the spinning units.
In general, each spinning unit of an open-end spinning machine includes a rotor with discharge openings through which air is ejected during rotation of the rotor. The rotor is surrounded by a casing or cover which is open at the bottom for the discharge of ejected air. The rotor has a frustoconical portion converging from the largest diameter portion of the rotor toward the axis thereof, and a short cylindrical portion defining a large center aperture. The casing has a sealing wall disposed about the cylindrical portion of the rotor in a manner allowing the rotor's rotation.
The spinning unit further includes a stationary means having a closure portion closing the center aperture defined by the rotor's cylindrical portion.
In such a spinning unit, upon rotation of the rotor, air present in the rotor is ejected through the discharge openings by the centrifugal force applied thereto, thus creating a negative pressure condition in the rotor, which condition causes a flow of air toward the inside of the rotor to be developed in a fiber inlet channel formed in the stationary means. Therefore, individual opened fibers as well as the flow of air are fed into the rotor through the inlet channel, and formed into a yarn at the largest diameter portion of the rotor. The resulting yarn is discharged from the rotor through an outlet channel formed in the stationary means.
In order to allow the negative pressure created in the rotor to operate on the fiber inlet channel of the stationary means as effectively as possible, a conventional spinning unit has been generally provided with a labyrinth between the short cylindrical portion of the rotor and the sealing wall of the casing. Such a labyrinth is shown in U.S. Pat. No. 3,874,751, for example. However, the labyrinth can result in various disadvantages including entrance of once discharged flies, dirt and so on into the labyrinth from the side of the casing, and much difficulty in forming the labyrinth in the associated portions.